Add plot recipes

[dlfivefifty]

[daanhb]

Plotting bounded domains could be somewhat generic if a domain supports a boundingbox function. That would allow for a grid on the bounding box, of which each point can be checked. We have the boundingbox function in FrameFun for other reasons.

Alternatively, some domains have a parameterization, which could be useful for plotting purposes as well. That would yield better resolution than a grid of points.

[daanhb]

Sounds like nowadays we could use package extensions for this purpose.